1. Field of the Invention
This invention relates to a liner utilized for preventing the outflow of water from a pipeline such as a sewer pipe and preventing the inflow of water into the pipeline, and a method for repairing the pipeline to prevent water leakage into and from the pipeline by using the liner.
2. Description of the Prior Art
As one of the prior art methods for repairing pipelines such as sewer pipes, water supply pipes, conduit tubes or the like, Japanese Utility Model Publication No. 62-18799 discloses disposing a liner having a rubber sleeve and a coil spring located within the sleeve such that the sleeve is pressed by the coil spring against the inner surface of the pipe defining a pipeline. However, in this method, the portions of the sleeve, which do not contact with the coil spring, are easily deformed by a force, such as ground water pressure, directed from the outside of the sleeve inward, so that ground water easily flows into the pipeline. To prevent this, the sleeve has to be thickened to improve its mechanical strength.
As one of the repair methods for preventing gas leakage from gas pipes, Japanese Utility Model Public Disclosure (KOKAI) No. 60-24993 discloses a method for disposing a liner having a rubber sleeve and an expandable band located inside the respective ends of the sleeve such that each end of the sleeve is pressed by the band against the inner surface of the pipe defining a pipeline. However, in this method, the axial center portion of the sleeve is also easily deformed by a force directed from the outside of the sleeve inward. Therefore, the mechanical strength of the axial center of the sleeve has to be improved to reinforce the mechanical strength thereof.
In order to solve these problems, the present inventors have proposed a method for preventing water leakage by use of a liner including a sheet-like base having a pair of overlapped portions into a spiral form to place one of the overlapped portions inside the other, and sheet-like rubber cut-off members disposed on the circumferential surface of the base.
In this method, the liner in its shrunken state is moved to the portion to be repaired within a pipe, and is then expanded, so that the liner is disposed to cover the inner surface of the pipe. When the liner is disposed at the pipe portion to be repaired, the cut-off members are pressed against the inner pipe surface by the base to prevent water leakage, and the base maintains the sleeve pressed against the inner surface of the pipe.
However, in the liner used in the above-described water leakage-prevention method, the cut-off members are butted in portions corresponding to the overlapped portions of the base. Consequently, leakage of water from the butted portion of the cut-off members and the overlapped portions of the base is not prevented.